The endogenous antioxidants vitamin E, vitamin C, and coenzyme Q (CoQ) are thought to have significant interactions in the maintenance of cellular redox state and in cellular protection form oxidative insult. The proposed project will determine the extent to which these compounds can interact to ameliorate or prevent functional brain aging in mice, when supplemented in two- and three-way combinations. In one experiment (Aim1), supplementation with the antioxidant combinations will be initiated in late life, at age when brain dysfunction is already present. A battery of behavioral tests will be used to estimate the ability of the antioxidant supplementation regimens to reverse age-related losses of cognitive functions (associative learning, working memory, and spatial learning) as well as losses of sensory and psychomotor functions (auditory and somatosensory responsiveness, reaction time, coordination, balance, muscle strength). The same battery of behavioral tests will be used to determine whether or not the antioxidant supplementation regimens can prevent functional losses if supplementation is initiated prior to development of age-related brain dysfunction (Aim2). To determine whether or not beneficial effects of the antioxidative regimens depend on their ability to reduce oxidative stress/damage (Aim 3), brains from the mice tested in the first two aims will be dissected into different regions for determining: (i) amounts of oxidative damage to proteins or lipids (protein carbonyls, thiobarbituric reactive substances), (ii) shifts in glutathione redox state and amounts of aminothiols, protein sulfhydryl and mixed disulfides and (iii) levels of CoQ, vitamin E and vitamin C. The aminothiols status and albumin-associated carbonyl content of plasma will be determined at different times during treatments (Aim 4) to determine whether or not plasma markers of oxidative stress/damage are useful predictors of the effects of antioxidant supplementation on cognitive/psychomotor performance. These studies will provide specific information about the nature of antioxidant regimens most likely to be beneficial against brain aging and will identify the ages at which benefits should be expected. Moreover, they will improve understanding of the neurological consequences of antioxidant supplementation that are most critical to the beneficial effects and may identify clinically useful biological markers predictive of successful treatment.